It has been well known that polyalkyleneimines are useful as an agent for enhancing filtration of water during the molding of paper sheet, an agent for heightening the yields of filtration, dye, pigment, very minute fibers, and as a flocculant for white water in the papermaking industry and as a flocculant and a dehydration-promoting agent for activated sludge in the treatment of plant effluent and sewage.
The polyalkyleneimines, however, do not easily admit of addition to molecular weight which constitutes itself one of the conditions essential for the uses mentioned above. Moreover, they are very expensive. When they are used as an agent for enhancing filtration of water and heightening yield in the papermaking operation, for example, they betray a disadvantage that they are effective only in the neutral range and do not produce any stable effect over a wide range of pH value.
As substances improved to eliminate the disadvantage, nitrogen-containing condenstaion products have been proposed as disclosed in the specification of DE 2,436,386. It is stated in this specification that when polyalkyleneimines are cross-linked with a polyalkylene glycol polychlorohydrin ether, there are obtained water-soluble nitrogen-containing condensation products which admit of addition to molecular weight, prove to be economic, and manifest their effect over a wide range of pH value.
Actually, however, the reaction of polyalkyleneimines with a polyethylene glycol polyhalohydrin ether proceeds slowly and the production of the condensate takes up much time. Further, the cross-linking reaction is neither controlled easily nor allowed to produce a condensate of a desired molecular weight. The condensation products consequently obtained, therefore, have a disadvantage that they are deficient in performance as a water-treating agent and they are barely obtained as an aqueous solution of a low concentration of resin. Moreover, the reaction has a disadvantage that it is required to be carried out at a uniform pH value to ensure stable production of the condensate and necessitates addition of an alkaline substance to the reaction system.
The water-soluble cross-linked nitrogen-containing condensation product obtained by the reaction of polyethylene glycol-polypropylene glycol polychlorohydrin with ethyleneimine has been also known in the art (specification of DE 2,638,955). This nitrogen-containing condensation product, however, possesses insufficient solubility, produces an aqueous solution of only low concentration of resin, and exhibits an insufficient performance as a water-treating agent.
This invention has originated in an urge to eliminate the problems suffered by the products of prior art and aimes to provide a method for quickly and safely producing by a simple procedure a cationic water-soluble resin transformable into an aqueous solution of high concentration over a wide ragne of molecular weight and a water-treating agent capable of manifesting a conspicuous effect thereof over a wide range of pH value.